Nov. 12, 2008
Watching Remnant Low of Maysak for New Signs of Life
Hurricane Season 2008: Maysak (Eastern Pacific)
Tropical Depression Maysak crossed its own path in the South China Sea earlier this week, making a "cyclonic loop." That means it traveled in one entire circle and crossed over a place it was before (on its earlier track northward). Now, the low pressure area that was once Maysak is being eyed closely by forecasters at the Joint Typhoon Warning Center for possible regeneration or total dissipation.
On Wednesday, Nov. 12, at 1100 Zulu Time (about 6 a.m. EST) forecasters at the Joint Typhoon Warning Center (JTWC) said that "Formation of a significant tropical cyclone is possible within 90 nautical miles either side of a line from 11.8 north 116.4 east to 9.9 north 113.1 east within the next 6 to 24 hours. Available data does not justify issuance of numbered tropical cyclone warnings at this time."
The JWTC did say that winds are circulating around 18-23 knots (20-26 mph), and there is a circulation center. The low was moving southwestward near 9 knots (10 mph). The low and its associated shower activity is near 11.4 degrees north latitude and 116.1 east longitude, or 345 nautical miles southwest of Manila, the Philippines. NASA's QuikScat satellite and the Windsat satellite revealed 20 knot (23 mph) winds in the low pressure area.
NASA's Quick Scatterometer satellite (QuikScat) can determine wind speed in a tropical cyclone by using microwaves to peer into the clouds. WindSat is a satellite-based polarimetric microwave radiometer on the Coriolis satellite, developed by the Naval Research Laboratory Remote Sensing Division and the Naval Center for Space Technology for the U.S. Navy and the National Polar-orbiting Operational Environmental Satellite System Integrated Program Office. WindSat is designed to demonstrate the capability of polarimetric microwave radiometry to measure the ocean surface wind vector from space. The WindSat/Coriolis mission was launched on a Titan II rocket from Vandenburg Air Force Base in January, 2003.
The JTWC also noted, "An upper level analysis indicates an improved upper level environment with light to moderate vertical wind shear (winds that tear a storm apart) and favorable difluence (A pattern of wind flow in which air moves outward (in a "fan-out" pattern)) aloft. That means the conditions are improving to allow storm regeneration, but forecasters are just waiting and watching closely.
Rob Gutro/Goddard Space Flight Center
Nov. 10, 2008
Tropical Depression Maysak West of the Philippines, Set to Make a Loop
Tropical Cyclone Maysak formed west of the Philippines, in the South China Sea and has stayed at sea, where it will dissipate. On Nov. 10, Maysak was heading southward to complete a "cyclonic loop." That means it traveled in one entire circle and crossed over a place it was before (on its earlier track northward).
Maysak formed on Nov. 7 in the open waters of the South China Sea, then tracked northwestward. Maysak was a typhoon on Nov. 8 when its sustained winds reached 55 knots (63 mph). On that date, Tropical Storm Maysak was located approximately 370 nautical miles west-northwest of Manila, Philippines.
Maysak's tropical storm status was limited. Forecasters at the Joint Typhoon Warning Center issued their last advisory on Maysak on Monday, Nov. 10 at 0000 Zulu Time (about 7 p.m. EST). At that time, a weakening Maysak had sustained winds near 25 knots (28 mph) and was moving south-southeast around 6 knots (7 mph). Maysak was a tropical depression, and was located about 280 nautical miles west-northwest of Manila, the Philippines, near 15.3 degrees north and 116.6 degrees east.
In the area where Tropical Depression Maysak is located, the region is experiencing extreme vertical wind shear (winds that tear a tropical cyclone apart) associated with a major shortwave trough (elongated area of low pressure) exiting China. That trough will continue to move east and further degrade the system over the next 24 hours.
NASA's Aqua Satellite Instrument Sees Maysak's Clouds
NASA's Atmospheric Infrared Sounder (AIRS) instrument on NASA's Aqua satellite has been keeping an eye on Maysak's cloud temperatures, and is watching them become less cold as the system continues to weaken. AIRS produced infrared the image, taken on Nov. 10 at 12:05 a.m. EST (5:05 UTC).
The infrared image shows the frigid cloud top temperatures, giving forecasters a clue to the storm's strength. The lowest temperatures (in purple) are associated with Maysak's high, cold cloud tops. Those areas are as cold as 220 degrees Kelvin or minus 63 degrees Fahrenheit (F) or colder. The blue areas are around 240 degrees Kelvin, or minus 27F.
The Joint Typhoon Warning Center uses cloud temperature as one factor in determining whether a tropical cyclone is strengthening. When cloud temperatures get colder, it means that clouds are getting higher. Building clouds indicate a lot of "uplift" in the atmosphere and stronger thunderstorms.
AIRS' infrared signal doesn't penetrate through clouds, so where there are clear skies AIRS reads the infrared (heat) signal from the ocean and land surfaces, revealing warmer temperatures (colored in orange and red). The orange temperatures are 80F (300 degrees Kelvin) or greater (the darker they are, the warmer they are). Tropical cyclones need sea surface temperatures of 80F to strengthen and maintain their strength. Tropical Depression Maysak is forecast to linger a couple of days in the South China Sea before dissipating.
Rob Gutro/NASA's Goddard Space Flight Center